Microlens arrays for light extraction enhancement in organic light-emitting diodes: A facile approach

The commonly studied architecture of organic light-emitting diodes (OLEDs) faces the obstacle of limited light outcoupling from the planar glass substrate, which greatly affects the device external efficiency. Introduction of microstructures is considered as an effective approach to extract photons trapped within the device. To reach this end, a two-steps fabrication technique based on breath figure patterns and replica molding is here presented. Through this approach elastomeric microlens arrays having different morphological features are obtainable in a fast and simple way. We show how the mere application of these patches on the external face of a conventional OLED leads to a neat efficiency enhancement up to 34%. An increase of light intensity at viewing angle between 30 and 60° is also demonstrated. These results are a proof of principle that improving the performance of an OLED by a non-lithographic surface modification strategy and without altering its functioning, is feasible.